Radiation and Free Radical Research Core There is growing evidence that oxidative events and free radicals are important in the initiation, growth, invasion, metastasis, prevention and treatment of cancer. The Radiation and Free Radical Research Core (RFRRC) was established to provide free radical and radiation biology expertise, reagents, technologies, and analysis for HCCC investigators doing basic, pre-clinical, and clinical research. The three basic services provided by the core are: 1) Ionizing radiation services (IRS) and phosphorimaging 2) Electron paramagnetic resonance (EPR) to measure oxygen free radicals, singlet oxygen, nitric oxide and the array of related oxidants 3) Antioxidant enzyme services (AES) to modify and measure molecules responsible for free radical formation and oxidative damage in cells such as anti-oxidant proteins and small molecular weight cellular thiols The RFRRC is unique in its ability to provide such knowledge, reagents and resources. While the expertise for the RFRRC is based in the Free Radicals and Cancer Biology Program, the RFRRC has users from all HCCC programs.